Hydraulic cushions for die pads of ram type presses



Dec. 29, 1964 F. M. WILLIAMSON HYDRAULIC CUSHIONS FOR DIE PADS OF RAMTYPE. PRESSES Filed April 27, 1962 2 Sheets-Sheet 1 INV EN TOR.

)Vay/ M 144752711501. BY

Dec- 29, 19 F. M. WILLIAMSON HYDRAULIC CUSHIONS FOR DIE PADS OF RAM TYPEPRESSES Filed April 27, 1962 2 Sheets-Sheet 2 INVENTOR. f/ay /y Ma47214022 BY 661% M 16 2 7 United States Patent 3,163,143 HYDRAULIClUSHlGNS FGR DE PADS @F RAM TYPE PREES Floyd M. Williamson, Detroit,Mich, assignor, by niesne assignments, to National Bank of Detroit,Detroit, Mich, a national banking association Filed Apr. 27, 1962, Ser.No. 1%,542 15 Claims. (Cl. 113-45) This invention relates to presseshaving hydraulic cushions for controlling movement of the die pads andhas particular relation to a new and improved hydraulic control systemfor controlling the hydraulic cushion.

The hydraulic control system of the present invention is designed tooffer a predetermined resistance to movement of the die pad upon closingof the press ram and is provided with an air pressure device actuatedduring the opening of the press ram for returning the die pad to itsextended position for stripping the work from the die.

A principal object of the invention is to provide a new and improvedhydraulic control circuit for the hydraulic cushion in a press having amovable die pad.

Another object of the invention is to provide a control system of thetype described having a means for delaying return movement of the diepad until after the press begins to open and including a booster unit toincrease the pressure in the hydraulic cushion for stripping the workfrom the die.

Other and further objects of the invention will be apparent from thefollowing description and claims and may be understood by reference tothe accompanying drawings, of which there are two sheets, which by wayof illustration show preferred embodiments of the invention and what Inow consider to be the best mode of applying the principles thereof.Other embodiments of the invention may be used without departing fromthe scope of the present invention as set forth in the appended claims.

In the drawings:

FIG. 1 is a schematic sectional view illustrating a hydraulic cushionfor a movable die pad and the control system for the hydraulic cushion;

FIG. 2 is an elevational view illustrating one form of actuating meansfor the controls;

FIGS. 3 and 4 show modified actuating means for the controls; and

FIG. 5 is a schematic view of a modified form of the invention.

In PEG. 1 of the drawing there is illustrated a portion of a ram typepress which includes a reciprocating ram carrying an upper die 12 and alower die'id mounted on a fixed bolster 1d. The die 14 is provided witha vertically reciprocable die pad 18 which is engaged by the work Ziiduring the working stroke of the press. A piston 22 is reciprocablewithin a cylinder 24 and the piston 22 and cylinder 24 provide ahydraulic cushion engaging the underside of the die pad 13 to controlits movement both during the working stroke of the press and uponopening of the press to strip the work from the die 14.

The control system includes a tank 36 containing hydraulic fluid underpressure. The tank is supplied with air under pressure through an airpressure line 32 to maintain the hydraulic fluid at a predeterminedrelatively low pressure in the tank, say, for example, 100 lbs. persquare inch. The hydraulic cushion cylinder 24 is provided with an inletand exhaust port 34 to which a line 36 is connected, with the other endof the line 36 communicating with a bore 38 in a valve block 49. Valveblock til is provided with a chamber 42 containing a pressure reliefvalve 44 which is reciprocable therein andnorrnally engages a valve seat46 under the influence of a spring 43 which is confined between thevalve member 44 and a washer 5i and an adjustingscrew 52 engages thewasher 5i so that f ice the strength of the spring 48 may be adjusted topermit the valve 44 to open when a predetermined pressure in the line 36is reached.

A passage 54 in the valve 2 i intersects the valve cham ber 42 and isconnected by means of the line 56 to the lower end of the supply tank'30. When the ram of the press descends, the movable die pad 18 which isengaged by the work is forced downwardly, thereby moving the piston 22downwardly in the cylinder 24 to force the hydraulic fiuid therein outthrough the line 36. The pressure relief valve 44 provides apredetermined resistance to such movement of the die pad and, as soon asthe pressure in the hydraulic cylinder 24 exceeds a predeterminedpressure, the valve 44 will open thereby allowing the hydraulic fiuid toflow through line 56 back to the supply tank 36. As soon as the ramcompletes its working stroke, the pressure relief valve id will closethereby blocking the return of hydraulic fluid from the tank 36 back tothe hydraulic cushion cylinder 24.

iieans comprising a booster unit 66 are provided for effecting the flowof hydraulic fluid back into the cylinder 2 under increased pressure toefiect return movement of the die pad 13 and strip the work from the die14. The

booster unit includes a booster cylinder having a piston 64 therein anda larger diameter cylinder 66 having a piston 63 therein, with thepistons 64 and 68 interconnected by a stem '76}. The booster cylinder 62is filled with hydraulic fluid from the. tank 3% through a line 72leading from the lower end of the tank fill to a passage 74- in a valvebody '76. A passage 78 intersects the passage 74 and is normally closedby a check valve 83 in the form of a ball located in a chamber 82 whichis intersected by a passage 84 leading to a bore 86 in the valve body76. The lower end of the bore Sr: communicates with the booster cylinder62 above the piston as therein. The booster cylinder is filled with thehydraulic fluid from the tank 39 through the passages described. Theupper end of the bore 36 is closed by a normally closed, balanced,positive shut-oil valve of the sleeve or spool type indicated at 38,which comprises a sleeve 99 located in a recess in the valve body 76 andsurrounded by an annular chamber 92 intersected by a passage 4 whichleads to a line 96. A valve member 98 is reciprocable within the sleeve9% and is biased by a spring me against a shoulder W2 which determinesthe normallyclosed position of the valve 83. The sleeve 9i) is providedwith annularly spaced radial ports 104 which provide communicationbetween the bore 86 and the line 'sd when the valve 83 is opened. Thepassage 74 communicates with the upper end of the sleeve 9%) so thatboth sides of the valve member 9%- are subjected to the pressureexisting in the supply tank 36.

The line as is connected to a passage 1% in the valve block 4% whichcommunicates with a passage 1% leading to the bore 33 and the line 36.The passage 1% is normally closed by a check valve lib, although thischeck valve maybe omitted if desired.

The lower end of the air cylinder 66 below piston 68 is provided with aport 112 leading to a control or pilot valve lid which includes a supplyline port 116, an exhaust line port 113, and a control lever 12% bymeans of which the cylinder port 112 may be connected either to theexhaust port 11% or the supply port 11d which is connected to a sourceof air under pressure, such as the upper end of pressure tank 34 or theair pressure suppiy line 32 -therefor. The control lever 12b is actuatedby a solenoid,

I to the cylinder ea.

movement. The electrical circuit into which the solenoid 122 isconnected may include a fixed contact 13%} and a normally open movablecontact 13?; carried by a pivoted arm 134 which is adapted to be engagedby a cam 135 carried by a shaft 138 which rotates with the crank of thepress. The cam 13s is adjusted on the shaft 138 so as to close thecontacts 139 and 132 at a predetermined time after the press ram beginsto open during each cycle of the press. When the contacts close, thesolenoid 122 is energized to shift the control valve 114 to connect thecylinder p0rt112 with the supply line 116, thereby to force the piston68 upwardly within the cylinder as thereby forcing the piston 64upwardly to force the hydraulic fluid therein through the bore 86 toshift the valve member 5% upwardly to open the radial ports 1%. As soonas valve member 98 moves sufiiciently to expose ports ids, by

,draulic fluid flows through line and passage 1%, past check valve 116,and through passage 138 and line back to the hydraulic cushion cylinder24 to force the piston 22 therein upwardly against the die pad 18 toreturn the die pad to its extended position, thereby stripping the workfrom the die 14. The relative size of the pistons 68 and 64 greatlyincreases the pressure in he hydraulic cushion cylinder 24 above thepressure at which the hydraulic fluid is normally maintained within thesupply tank 3%, thereby insuring return of the die pad 13 and efiicientstripping of the work from the die. The time interval during which theunit 6% remains energized is determined by the length of the cam 13s. Assoon as the contacts 136 and 132 are opened, the solenoid isde-energized and the control lever 124i is then shifted by the spring124 to connect the cylinder port 112 with the exhaust line 118 therebyallowing the booster piston 63 to return to its lower position as thecylinder olis again filled with hydraulic fluid from the tank 3% in themanner described. The valve member 3 will also close at this time sinceit is subjected to equal hydraulic pressures on its opposite sides andis urged to itsclosed position by the spring tea.

The connection between the supply tanlr 351 and the hydraulic cushioncylinder 2% is normally closed by the valve 88 and, since this valve isa balanced valve, the spring 166) may be very light to maintain suchvalve in its normally closed position. Since the valve $8 is in thefluid connection between the tank Elli and the cylinder 24, the returnof the die pad 18 will be controlled by the opening of the valve 88 andthis in turn depends upon the setting of the cam 13s.

Instead of using the solenoid actuated pilot valve 114, a spool typenormally closed pilot valve 28%, as shown in FIG. 3, actuated directlyby the earn 135 may be used for controlling the return of the die pad.in this case the valve Zilll, when closed, ports the line 112communicating with cylinder as with line 113 leading to atmosphere,while the movable valve element 2&2. is normally positioned by thespring 2% so as to shut oil the flow of air under pressure from the airsupply line 1% to the passage 112. When the earn 13% engages the rolleron the follower arm 2% carried by the sliding valve member 2 32, thevalve member ZilZ will be shifted to a position to shut oft theatmospheric port and to establish communication between the air pressureline 112 and the line ltd leading The spring 2&4 causes the roller onthe arm 2&8 to follow the earn 136. This type of valve control is likethat shown in my prior copending application Serial;No. 768,889, filed()ctober 22., 1958, for. By-

' draulic Press, Ram Cushion.

FIG. 4 sh ws a normally closed rotary pilot valve V as shown in FIG. 1arranged so as to be actuated directly by cam 13%. p

In the arrangement of FlG. 1, the pressure which can be developed uponthe encrgization of the booster unit so is limited by the pressuresetting of the pressure relief valve 4% In some cases it is necessary ordesirable to provide a higher pressure in the hydraulic cushion on the12* roke than on the downstrolre, and this may be achieved with the isystem illustrated in F1 5 where the pressure relief valve is separatedfrom the discharge side of the booster unit 166.

in the system as disclosed in FlG. 5 hydraulic fluid under the pressureprevailing in the tank 39 is supplied through the hydraulic fluidpressure line 1.72 to the valve unit indicated generally at 171. Thevalve unit 171 is quite similar to the corresponding valve of the systemin FIG. 1 and includes a passage 178 communicating with the line 172, acheck valve 188 in the passage 1'78, and a passage 186 w rich at one endcommunicates with the discharge cylinder 162 of the booster 1%. Theother end of the passage 186 communicates with a valve chamber in theunit 171, the valve chamber having disposed therein a valve sleeve 15?;and a valve piston 19% biased to seat on the port around the upper endof passage res under the influence of spring 1%. Thus under the pressureprevailing in the tank 3%, hydraulic fluid is supplied through the line172 past the check valve 1% to the passage 136 and to the boostercylinder 162.

When the piston valve member 1% is moved upwardly in response to thedischarge of hydraulic fluid from the booster cydnder 162, it uncoversports 2% in the sleeve 138 which communicate with the space externallyof the sleeve res, which in turn communicates with a passage 292. in theunit r71. At its upper end the passage 292 communicates with a hydraulicfluid pressure conduit 2&4 which leads to the hydraulic cylinder 24 ofthe hydraulic cushion. Thus, when the ports 2 38' are uncovered,hydraulic rluid under the pressure prevailing in the tank 33* or underthe discharge pressure of the booster 166 will be supp ed to thecylinder 24 of the hydraulic cushion for biasing the piston 22 againstthe pad 1". When the piston valve 1% moves upwardly in the sleeve 188,it closes ports 2% in the sleeve 83 which normally provide opencommunication between the passage 204 and a hy draulic pressure line2.62% which leads to the pressure relief valve indicated generally at249.

Thus the energization of the booster res according to any of thearrangements disclosed in FIGS. l4 inclusive will not on I establishcommunication between the tank and the hydraulic cylinder 24 of thehydraulic cushion, but it will also shut off the communication betweenthe hydraulic cylinder 24 and the pressure relief valve 24%. Thepressure relief valve 24% is like the pressure relief valve ill oiPlG. 1. Thus with the arrangement illustrated in Flt 5, it is possibleto develop substantially higher pressures on the upstroke of the pressram than on the downstrolie since the pressure relief valve is separatedfrom the discharge side of the booster 16%. After the de-energization ofthe booster tea, the piston valve 19% will return to its seat as shownin FIG. 5. The system as illustrated in FIG. 5 other respects willoperate as described in connection with the systems illustrated in F165.l4.

This application is a continuation-in-part oi my prior copendingapplication Serial No. 84,900, filed January 25,

961, now abandoned for Hydraulic Cushions for Die i ads of Ram TypePresses, which is a continuation-inpart of my prior cop-endingapplication Serial No. 832,720, lied August lb, 1959, issued as PatentNo. 3,089,375, for lydraulically Actuated Piercing Unit, which is acontinuation-.n-part of my now abandoned application Serial No. 788,544,filed January 23, 1959, for l-lydraulically Actuated Piercing Unit.

While l have illustrated and described preferred embodiments of myinvention, it is understood that these are capable of modification, andI therefore do not wish to be limited to the precise details set forthbut desire to avail myself for such changes and alterations as fallwithin the purview of the following claims.

I claim:

1. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeflfect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein arranged toreact against said pad, a control system for controlling return movementof said pad comprising a tank separate from said cylinder and containinghydraulic fluid under regulated pressure, a hydraulic fluid connectionbetween said tank and one end of said cylinder through which hydraulicfluid from said tank is supplied to said cylinder, said connectionincluding a valve having a spring biasing said valve to its closedposition so as to prevent fluid flow from said tank to said cylinderwhen said valve is closed, means connecting the opposite sides of saidvalve to said tank so that both sides of said valve are exposed to thepressure of the hydraulic fluid in said tank, control means connected tosaid valve and ac tuated by the press after the press begins to open foropening said valve to allow hydraulic fluid to flow through saidconnection to said cylinder to effect return movement of said pad, afluid return line through which hydraulic fluid displaced from said oneend of said cylinder upon closing of the press is returned to said tank,and a pressure relief valve in said return line providing resistancesubstantially higher than tank pressure to the return flow of suchdisplaced fluid so as to resist movement of said die pad in said onedirection and adapted to open when the pressure in said cylinder exceedsa predetermined pressure.

2. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press ram and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeffect return movement of the pad upon opening of the press ram, saidhydraulic cushion including a cylinder and a piston therein arranged toreact against said pad, a control system for controlling movement ofsaid pad comprising a tank separate from said cylinder and containinghydraulic fluid under regulated pressure, a booster cylinder, aunidirectional hydraulic fluid connection between said tank and boostercylinder through which hydraulic fluid flows under tank pressure fromsaid tank to said booster cylinder when said booster is inactive, aunidirectional fluid flow passage connecting said booster cylinder andtank with one end of said hydraulic cushion cylinder, a piston in saidbooster cylinder, a control valve connecting said booster cylinder to asource of pressure fluid and adapted when open to actuate said boosterpiston in a direction to increase the pressure in said hydraulic cushioncylinder to effect return movement of said pad, control means connectedto said valve and actuated by the press for opening said valve toactuate said booster piston at a predetermined time during the openingportion of each cycle of the press, a normally closed valve in saidpassage etween said tank and said hydraulic cushion cylinder and havingits opposite sides subjected to the pressure of the hydraulic fluid insaid tank, said normally closed valve being opened by fluid dischargedfrom said booster cylinder upon actuation of said booster piston, aliuid'return line con ected into said passage and to said tank throughwhich hydraulic fluid displaced from said hydraulic cushion cylinderflows to said tank upon closing of the press, and a pressure reliefvalvein said return line providing for resistance to the flow of suchdisplaced fluid so as to resist movement of said die pad in said onedirection and adapted to open when the pressure in said hydraulic tcushion cylinder exceeds a predetermined pressure.-

3. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press, a hydraulic cushion reactingagainst said pad to resist such movement of said padand to effect return'movement of the pad upon opening of the press said hydraulic cushionincluding a cylinder and a piston therean arranged to react against saidpad, a control system for controlling movement of said pad comprising atank through said passage to said one end of said hydraulic cushioncylinder to etlect return movement of said pad, control means connectedto said valve and actuated by the press for opening said valve toactuate said booster piston at a predetermined time during the openingportion of each cycle of the press, a normally closed valve insaidpassage between said tank and said hydraulic cushion cylinder andcomprising means defining a valve chamber communicating at one end withsaid booster cylinder, said passage intersecting said valve chamber, avalve member reciprocable in said valve chamber and a spring biasingsaid valve member to a position closing said passage, means connectingthe other end of said valve chamber with said tank so that both sides ofsaid valve member are exposed to the pressure of the hydnaulic fluid insaid tank, said valve member being rnoV- able against said spring toopen said passage upon actuation of said booster piston, a return linethrough which hydraulic fluid displaced from said one end of saidhydraulic cushion cylinder flows to said tank upon closing of the press,and a pressure relief valve in said return line press and a hydrauliccushion reacting against said pad to resist such movement of said padand to eifect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein arranged toreact against said pad, a control system for controlling return movementof said pad comprising a tank separate from said cylinder. andcontaining hydraulic fluid under pressure, a booster cylinder, athydraulic fluid connection between said tank and booster cylinder, apassage connecting said booster cylinder and tank with one end of saidhydraulic cushion cylinder, a piston in said booster cylinder, a controlvalve connecting said booster cylinder to a source of pressure fluid andadapted when open to actuate said booster piston in a direction to forcethe hydraulic fluid in said booster cylinder through said passage tosaid one end of said hydraulic cushion cylinder to effect returnmovement of said pad, control means connected to saidvalve and actuatedby the press for opening said valve to actuate said booster piston apredetermined time'interval after the press begins to open during eachcycle of the press, a normally closed valve in said passage between saidtank and said hydraulic cushion cylinder and comprising a sleevecommunicating at one end with said-booster cylinder and having radicalports therein providing a part of said passage,a valve memberreciprocable in said sleeve and a spring biasing said valve member to aposition closing said posts, and means connecting-the other end of saidsleeve with said tank .so that both sides of said valve member areexposedto the pressure'of the hyduaulic fluid'in said. tank, said valvemember being movable against said spring to open said ports uponactuation of said booster piston, and a pressure relief controlled fluidreturn line leading. "from said one end of said hydraulic cushioncylinder to said "tank providing resistance to movement of said die padupon closing of the press'ram and adapted to open Whenthe pressure insaid hydraulic cushion cylinder exceedsa predetermined pressure. 7 5. Ina press having a'movable pressurepad arranged so as to' be moved in onedirection upon closing of the i H press and a hydraulic cushion reactingagainst said pad to resist such movement of said pad and to eifectreturn movement of the pad upon opening of the press, said hydrauliccushion including a cylinder and a piston therein arranged to reactagainst said pad, a control system for controlling return movement ofsaid pad comprising a tank separate from said cylinder and containinghydraulic fluid under regulated pres-sure, a hydraulic fluid connectionbetween said tank and one end of said cylinder through which hydraulicfluid is supplied from said tank to said cylinder, a normally closedvalve in said connection, mean connecting the opposite sides of saidvalve to said tank so that both sides of said valve are exposed to thepressure of the hydraulic fluid in said tank, control means for saidvalve actuated by the press for opening said valve to allow hydraulicfluid to flow through said connection to said one end of said cylinderat a predetermined time during the opening portion of each cycle f thepress, and a pressure relief controlled fluid return line leading fromsaid one end of said hydraulic cushion cylinder to said tank providingresistance to movement of said die pad upon closing of the press ram andadapted to open when the pressure in said hydraulic cushion cylinderexceeds a predetermined pressure.

6. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeflect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein arranged toreact against said pad, a control system for controlling return movementof said pad comprising a tank separate from said cylinder and containinghydraulic fluid under pressure, a hydraulic fluid connection betweensaid tank and one end of said cylinder whereby hydraulic fluid issupplied from said tank to said cylinder, a normally closed valve insaid connection and a spring biasing said valve to its closed position,meansconnecting the opposite sides of said valve to said tank so thatboth sides of said valve are exposed to the pressure of the hydraulicfluid in said tank, control means for said valve actuated by the pressfor opening said valve to allow hydraulic fluid to flow through saidconnection to said cylinder to increase the pressure in said cylinder toeffect return movement of said pad; said control -means being operableto open said valve a predetermined time interval after the press beginsto open during each cycle of the press, and a pressure relief fluidcontrolled return line leading from said 'one end of said hydrauliccushion cylinder to said tank providing resistance to movement of saiddie pad upon closing of the press ram and adapted to open when thepressure in said hydraulic cushion cylinder exceeds a predeterminedpressure.

7. In a press having amovable pressure pad arranged so'as to be moved inone direction upon closing of the press ram and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeltect return movement of the pad upon opening of the press ram, saidhydraulic cushion including a cylinder. and a piston therein arranged toreact against said pad, a tank separate from said cylinder andcontaining hydraulic fluid under regulated pressure, a hydraulic fluidconnection between said tank and one end of said cylinder through whichhydraulic fluid is supplied to said cylinider, a normally closedshut-off valve in said connection which in'its closed position preventsfluid flow in both directions, a pressure relief by-pass around saidshut-oft valve providingresistance to movement of said die pad uponclosing of the-press ram and adapted to open when thepressure in saidhydraulic cushion cylinder exceeds a. predetermined pressure, andcontrol means for said shut-off valve, said control means being,actuated by the press for-opening said shu -off valve to allow hydrauliccame fluid to flow through said fluid connection to said one end of saidcylinder to eiifect return movement of said pad, said control meansbeing operable to open said shutoff valve a predetermined time intervalafter the press ram begins to open dur ng each cycle of the press.

8. in a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press ram and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeffect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein arranged toreact against said pad, a control system for controlling return movementof said pad comprising a tank separate from said cylinder and containinghydraulic fluid under. pressure, a hydraulic fluid connection betweensaid tank and one end of said cylinder whereby hydraulic fluid issupplied to said cylinder, a normally closed shut-oil valve in saidconnection, the opposite sides of said valve being connected to saidtank so that both sides of said valve are normally subjected to thepressure of the hydraulic fluid in said tank, means for opening saidshut-oil valve whereby hydraulic fluid is supplied through saidconnection to said cylinder at a predetermined time during the openingportion of each cycle of the press, a pilot valve operated by a camdriven with the press for controlling said last-mentioned means, and apressure relief controlled return line leading from said one end of saidhydraulic cushion cylinder to said tank providing resistance to movementof said die pad upon closing of the press ram and adapted to open whenthe pressure in said hydraulic cushion cylinder exceeds a predeterminedpressure.

9. in a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeflect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein, a controlsystem for controlling return movement of said pad comprising a tankseparate from said cylinder and containing hydraulic fluid underpressure, a hydraulic fluid connection between said tank and one end orsaid cylinder whereby hydraulic fluid is supplied to said cylinder, anormally closed shut-off valve in said connection, means for openingsaid valve whereby hydraulic fluid is supplied to said one end of saidcylinder at a predetermined time during the opening portion of eachcycle of the press, a cam driven with the press, a pilot valve operatedby said cam for controlling the supply of fluid pressure to said valveopening means, and a pressure relief controlled return line leading fromsaid one end of said hydraulic cushion cylinder to said tank providingresistance to movement of said die pad upon closing of the press ram andadapted to open when the pressure in said hydraulic cushion cylinderexceeds a predetermined pressure.

10. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeilect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein, a control,system for controlling return movement of said pad comprising a tankseparate from said cylinder and containing hydraulic fluid underpressure, a hydraulic fluid connection between said tank and one end ofsaid cylindn' through which hydraulic fluid is supplied to saidcylinder, a normally closed positive shut-oi? valve in said connection,means independent of the pressure in said tank for opening said valvewhereby hydraulic fluid is supplied to said cylinder at a predeterminedtime during the opening portionof each cycle of the press, and apressure relief controlled return line leading from said one end of saidhydraulic cushion cylinder to said tank providing resistance to movementof said die pad upon closing of the press ram and adapted to open whenthe pressure in said hydraulic cushion cylinder exceeds a predeterminedpressure.

11. Apparatus according to claim wherein said means includes a pressurebooster associated with said hydraulic fluid connection and operable forincreasing the pressure of the hydraulic fluid supplied to saidcylinder.

12. Apparatus according to claim 11 wherein said normally closed valveis operatively disposed between said booster and said pressure reliefvalve.

13. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press ram and a hydraulic cushionreacting against said pad to resist such movement of said pad and toeffect return movement of the pad upon opening of the press, saidhydraulic cushion including a cylinder and a piston therein, a controlsystem for controlling return movement of said pad comprising a tankseparate from said cylinder and containing hydraulic fluid underpressure, a hydraulic fluid connection between said tank and one end ofsaid cylinder through which hydraulic fluid is supplied to saidcylinder, a normally closed positive shut-01f valve in said connection,pressure booster means for opening said shutoff valve whereby hydraulicfluid is supplied at increased pressure through said connection to saidone end of said cylinder at a predetermined time during the openingportion of each cycle of the press, and a pressure relief controlledreturn line leading from said one end of said hydraulic cushion cylinderto said tank providing resistance to movement of said die pad uponclosing of the press ram and adapted to open when the pressure in saidhydraulic cushion cylinder exceeds a predetermined pressure.

14. Apparatus according to claim 13 wherein said normally closed valvepressure isolates said pressure relief valve from said pressure boostermeans.

15. In a press having a movable pressure pad arranged so as to be movedin one direction upon closing of the press ram and a hydraulic cushionarranged to react against said pad to effect return movement thereofupon opening of the press ram, said hydraulic cushion including acylinder and a piston therein, a tank containing hydraulic fluid underpressure, a hydraulic fluid connection between said tank and saidcylinder through which hydraulic fluid is supplied to said cylinder, anormally closed shut-off valve in said connection which in its closedposition prevents fluid flow from said tank to said cylinder and fromsaid cylinder to said tank, a pressure relief by-pass around saidshut-01f valve providing resistance to return of hydraulic fluid to saidtank so as to resist movement of said die pad upon closing of the pressram and adapted to open when the pressure in said hydraulic cushioncylinder exceeds a predetermined amount, and control means actuated bythe press for opening said shut-ofl? valve to allow hydraulic fluid toflow through said fluid connection to said cylinder to efiect returnmovement of said pad after the press ram begins to open during eachcycle of the press.

References Cited by the Examiner UNITED STATES PATENTS 1,745,549 2/ 30Marghitan 113-46 2,172,853 9/39 Rode 267-1 2,394,636 2/46 Rode 113-452,403,912 7/46 Doll 267-1 2,584,339 2/52 Georgetf 267-1 2,890,669 6/59Williamson 267-1 2,918,272 12/59 Williamson 267-1 CHARLES W. LANHAM,Primary Examiner.

NEDWIN BERGER, Examiner.

1. IN A PRESS HAVING A MOVABLE PRESSURE PAD ARRANGED SO AS TO BE MOVEDIN ONE DIRECTION UPON CLOSING OF THE PRESS AND A HYDRAULIC CUSHIONREACTING AGAINST SAID PAD TO RESIST SUCH MOVEMENT OF SAID PAD AND TOEFFECT RETURN MOVEMENT OF THE PAD UPON OPENING OF THE PRESS, SAIDHYDRAULIC CUSHION INCLUDING A CYLINDER AND A PISTON THEREIN ARRANGED TOREACT AGAINST SAID PAD, A CONTROL SYSTEM FOR CONTROLLING RETURN MOVEMENTOF SAID PAD COMPRISING A TANK SEPARATE FROM SAID CYLINDER AND CONTAININGHYDRAULIC FLUID UNDER REGULATED PRESSURE, A HYDRAULIC FLUID CONNECTIONBETWEEN SAID TANK AND ONE END OF SAID CYLINDER THROUGH WHICH HYDRAULICFLUID FROM SAID TANK IS SUPPLIED TO SAID CYLINDER, SAID CONNECTIONINCLUDING A VALVE HAVING A SPRING BIASING SAID VALVE TO ITS CLOSEDPOSITION SO AS TO PREVENT FLUID FLOW FROM SAID TANK TO SAID CYLINDERWHEN SAID VALVE IS CLOSED, MEANS CONNECTING THE OPPOSITE SIDES OF SAIDVALVE TO SAID TANK SO THAT BOTH SIDES OF SAID VALVE ARE EXPOSED TO THEPRESSURE OF THE HYDRAULIC FLUID IN SAID TANK, CONTROL MEANS CONNECTED TOSAID VALVE AND ACTUATED BY THE PRESS AFTER THE PRESS BEGINS TO OPEN FOROPENING SAID VALVE TO ALLOW HYDRAULIC FLUID TO FLOW THROUGH SAIDCONNECTION TO SAID CYLINDER TO EFFECT RETURN MOVEMENT OF SAID PAD, AFLUID RETURN LINE THROUGH WHICH HYDRAULIC FLUID DISPLACED FROM SAID ONEEND OF SAID CYLINDER